1. Field of the Invention
The present invention relates to an adhesive composition that can be used in the production of semiconductor devices, is ideal for use within resin-molded semiconductor packages, exhibits excellent filling of substrates with finely patterned surfaces, and also has a low elastic modulus and high adhesive strength, and also relates to an adhesive film that comprises such an adhesive composition, and a method of producing a semiconductor device that uses such an adhesive film.
2. Description of the Prior Art
In the production of a semiconductor device, a large diameter silicon wafer with IC circuits formed thereon is cut into semiconductor chips in a dicing (cutting) step, a semiconductor chip is mounted to a lead frame by thermocompression bonding or the like using a liquid adhesive (a die bonding material), wire bonding is conducted between the electrodes, and the entire structure is then sealed in order to improve the handling properties and protect the device from the external environment. Examples of suitable sealing techniques include airtight sealing such as metal sealing and ceramic sealing, and non-airtight sealing using resins. Transfer molding using resins is the most widely used technique as it is inexpensive and offers excellent applicability to mass production. However, despite these advantages, resin-molded packages suffer from inferior levels of moisture resistance, heat resistance, thermal stress relaxation, and heat radiation.
Furthermore, in recent years, as a result of the trends towards smaller and increasingly multifunctional electrical and electronic equipment, the demands for increasingly sophisticated electronic components have lead to finer wiring and increased wiring density within semiconductor devices. As a result of this increase in semiconductor chip size, and the use of semiconductor devices that have structures of the same size as the chip (CSP) (which employ area array bonding and have no lead frame), or structures that employ chip layering (such as stacked CSP and SiP), the thermal shock (stress) during the packaging (PKG) of these devices is becoming a significant problem.
Moreover, in the processes for mounting these semiconductor devices onto a printed circuit board, the reflow resistance required for lead-free solders has reached a considerably high temperature (265° C.), which is also problematic. Accordingly, there is a strong need to ensure optimization and maximum performance of the materials used in these processes. Amongst the various packaging materials, the properties of die bonding materials in particular can be controlled and varied over a relatively wide range, and can therefore be readily adapted to meet these needs. Specifically, a die material having a low elastic modulus and high levels of adhesive strength and heat resistance, which is also capable of withstanding harsh thermal shock (stress) is required as the die bonding material.
Furthermore, miniaturization is also being demanded of the support substrates onto which the semiconductor chips are mounted. The use of liquid adhesives can cause problems, including contamination of electrodes caused by liquid adhesive exuding out around the edges of the chip during chip mounting, and wire bonding problems due to chip tilt caused by uneven thickness within the adhesive layer. Accordingly, the development of adhesive films capable of overcoming these problems is also keenly sought.
Examples of conventional adhesives include low elastic modulus materials in which siloxane structures have been introduced into highly heat-resistant polyimide and polyamide resins. Publications such as JP 3-189127 A (patent reference 1) disclose siloxane-modified polyamideimides, but the elastic modulus of such resins is still not low enough, and the adhesion of such resins to substrates is not entirely satisfactory.
JP 10-60111 A (patent reference 2) discloses the blending of a compound having two or more maleimide groups with a siloxane-modified polyamideimide, thereby improving the high-temperature properties, but the adhesive strength of this resin composition is poor.
Furthermore, JP 7-224259 A (patent reference 3) and JP 8-27427 A (patent reference 4) disclose heat-resistant adhesive films comprising a polyimide silicone and an epoxy resin, and these resins offer excellent adhesion, a low elastic modulus, and excellent heat resistance. However, although these adhesive films offer improved adhesive strength, their filling of substrates with fine surface irregularities is unsatisfactory. As a result, small voids can develop during die attachment, and these voids can lead to peeling of the adhesive film, meaning the films tend to suffer from reliability problems. Furthermore, if a large quantity of an inorganic filler is added in order to improve the reliability by reducing the coefficient of water absorption and the coefficient of linear expansion, then the performance of the adhesive during low-temperature lamination to semiconductor wafers at temperatures of 100° C. or lower tends to deteriorate.
[Patent Reference 1] JP 3-189127 A
[Patent Reference 2] JP 10-60111 A
[Patent Reference 3] JP 7-224259 A
[Patent Reference 4] JP 8-27427 A
[Patent Reference 5] JP 2003-193016 A